#include "rpigpio.h"

int
GPIOExport(int pin)
{
#define BUFFER_MAX 3
  char buffer[BUFFER_MAX];
  ssize_t bytes_written;
  int fd;

  fd = open("/sys/class/gpio/export", O_WRONLY);
  if (-1 == fd) {
    fprintf(stderr, "Failed to open export for writing!\n");
    return(-1);
  }

  bytes_written = snprintf(buffer, BUFFER_MAX, "%d", pin);
  write(fd, buffer, bytes_written);
  close(fd);
  return(0);
}

int
GPIOUnexport(int pin)
{
  char buffer[BUFFER_MAX];
  ssize_t bytes_written;
  int fd;

  fd = open("/sys/class/gpio/unexport", O_WRONLY);
  if (-1 == fd) {
    fprintf(stderr, "Failed to open unexport for writing!\n");
    return(-1);
  }

  bytes_written = snprintf(buffer, BUFFER_MAX, "%d", pin);
  write(fd, buffer, bytes_written);
  close(fd);
  return(0);
}

int
GPIODirection(int pin, int dir)
{
  static const char s_directions_str[]  = "in\0out";

#define DIRECTION_MAX 35
  char path[DIRECTION_MAX];
  int fd;

  snprintf(path, DIRECTION_MAX, "/sys/class/gpio/gpio%d/direction", pin);
  fd = open(path, O_WRONLY);
  if (-1 == fd) {
    fprintf(stderr, "Failed to open gpio direction for writing!\n");
    return(-1);
  }

  if (-1 == write(fd, &s_directions_str[IN == dir ? 0 : 3], IN == dir ? 2 : 3)) {
    fprintf(stderr, "Failed to set direction!\n");
    return(-1);
  }

  close(fd);
  return(0);
}

int
GPIORead(int pin)
{
#define VALUE_MAX 30
  char path[VALUE_MAX];
  char value_str[3];
  int fd;

  snprintf(path, VALUE_MAX, "/sys/class/gpio/gpio%d/value", pin);
  fd = open(path, O_RDONLY);
  if (-1 == fd) {
    fprintf(stderr, "Failed to open gpio value for reading!\n");
    return(-1);
  }

  if (-1 == read(fd, value_str, 3)) {
    fprintf(stderr, "Failed to read value!\n");
    return(-1);
  }

  close(fd);

  return(atoi(value_str));
}

int
GPIOWrite(int pin, int value)
{
  static const char s_values_str[] = "01";

  char path[VALUE_MAX];
  int fd;

  snprintf(path, VALUE_MAX, "/sys/class/gpio/gpio%d/value", pin);
  fd = open(path, O_WRONLY);
  if (-1 == fd) {
    fprintf(stderr, "Failed to open gpio value for writing!\n");
    return(-1);
  }

  if (1 != write(fd, &s_values_str[LOW == value ? 0 : 1], 1)) {
    fprintf(stderr, "Failed to write value!\n");
    return(-1);
  }

  close(fd);
  return(0);
}

